A3.2

introgression

a process by which hybrids form over many generations, instead of having an equal share of the origal two species, there is an unequal contribution from each spiecies

backcrossing

the hybrid organism reproduces with one of the original parents species to produce offspring

difficulties in traditional hierarchy randking

highly subjective, does not show evolutionary relationships, introgression, moving organisms within the hierarchy

cladistics

a natural system of classification for grouping taxa, based on characteristics that have evolved most recently